Re: [Lsr] 【Responses for Comments on PUAM Draft】RE: IETF 112 LSR Meeting Minutes

[Aijun Wang <[e-mail]>]

Hi, Robert:

Aijun Wang
China Telecom

> On Nov 23, 2021, at 19:42, Robert Raszuk <[e-mail]> wrote:
> 
> 
> 
> > For IGP solution, the BFD is not required. 
> 
> Excuse me ? 
> 
> BFD is used on vast majority of the WAN links today as those links are not always dark fiber such that you can detect LOS. Those WAN links are (unfortunately) emulated circuits which require BFD to detect failure in a reasonable time. 
> 
> I hope you are not talking about IGP hellos or BGP keepalives here. 
> 
> We are talking PE-P or PE-RR. 

[WAJ] Once there is a link/node failure, upon receiving the updated LSA, the ABR can calculate the missed prefixes within its attached area, as described in https://datatracker.ietf.org/doc/html/draft-wang-lsr-prefix-unreachable-annoucement-08#section-4

> 
> Thx,
> R.
> 
> 
> 
>> On Tue, Nov 23, 2021 at 12:38 PM Aijun Wang <[e-mail]> wrote:
>> Hi, Robert:
>> 
>> Aijun Wang
>> China Telecom
>> 
>>>> On Nov 23, 2021, at 18:04, Robert Raszuk <[e-mail]> wrote:
>>>> 
>>> 
>>> 
>>> > When the node is failed, or is detached from the network, it can’t send the BGP update to other peers already.
>>> 
>>> LOL ... that's given. Same for IGP too. 
>>> 
>>> The UPDATE will be generated by the BGP peer of such node - typically RR. And if you run BFD on that session it can be as fast as loosing IGP adj to an IGP neighbour of the failing node. 
>> [WAJ] Then you depend again the BFD session which there is configuration overhead. For IGP solution, the BFD is not required. 
>> And, for tunnels situations, where you configure the monitor peer?
>> 
>> Aijun Wang
>> China Telecom
>> 
>>> 
>>> Cheers,
>>> R.
>>> 
>>> 
>>> 
>>> 
>>>> On Tue, Nov 23, 2021 at 10:03 AM Aijun Wang <[e-mail]> wrote:
>>>> Hi, Robert:
>>>> 
>>>>  
>>>> 
>>>> When the node is failed, or is detached from the network, it can’t send the BGP update to other peers already.
>>>> 
>>>> And, as we have discussed, the potential usage of such information is not only BGP, but may be tunnel endpoints.
>>>> 
>>>> Yes, I agree, the light speed is the same.
>>>> 
>>>>  
>>>> 
>>>>  
>>>> 
>>>> Best Regards
>>>> 
>>>>  
>>>> 
>>>> Aijun Wang
>>>> 
>>>> China Telecom
>>>> 
>>>>  
>>>> 
>>>> From: [e-mail] <[e-mail]> On Behalf Of Robert Raszuk
>>>> Sent: Tuesday, November 23, 2021 4:40 PM
>>>> To: Aijun Wang <[e-mail]>
>>>> Cc: Les Ginsberg (ginsberg) <[e-mail]>; Gyan Mishra <[e-mail]>; Christian Hopps <[e-mail]>; Tony Li <[e-mail]>; lsr <[e-mail]>; Acee Lindem (acee) <[e-mail]>; Tony Przygienda <[e-mail]>
>>>> Subject: Re: [Lsr] 【Responses for Comments on PUAM Draft】RE: IETF 112 LSR Meeting Minutes
>>>> 
>>>>  
>>>> 
>>>> Aijun,
>>>> 
>>>>  
>>>> 
>>>> > or lose the fast convergences
>>>> 
>>>>  
>>>> 
>>>> Putting aside all the drawbacks already discussed, what makes you think that flooding LSPs or LSAs across tens of hops over 2 or maybe soon 8 areas would be any faster then sending BGP UPDATE message(s) across 2-3 RRs ? 
>>>> 
>>>>  
>>>> 
>>>> Assume you need to detect the failure and react to it in your RP/RE regardless how it is signalled. If triggered by ABRs you not only need to detect the failure of a node, but also flood it locally within the local area. 
>>>> 
>>>>  
>>>> 
>>>> Light propagation speed last time I checked does not seems to be different for BGP vs OSPF/ISIS packets. 
>>>> 
>>>>  
>>>> 
>>>> Thx,
>>>> 
>>>> R.
>>>> 
>>>>  
>>>> 
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